Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
Maintenance of nuclear architecture is crucial for gene regulation, cell proliferation and tissue development. However, during every open mitosis and meiosis, chromosomes are exposed to cytoskeletal forces until they are fully reassembled into mature nuclei. Here we discuss our recent study of nuclear assembly in Xenopus egg extracts, where we showed that the DNA binding protein Developmental pluripotency associated 2 (Dppa2) directly inhibits microtubule polymerization during nuclear formation, and that this is essential for normal nuclear shape and replication. We explore mechanisms by which microtubule dynamics could regulate nuclear formation and morphology, and discuss the importance of both spatial and temporal regulation of microtubules in this process. Moreover, expression of Dppa2 is limited to the early embryo and pluripotent tissues, and we highlight the specific demands of mitosis in these often rapidly dividing cells, in which telophase nuclear assembly must be expedited and may facilitate developmental changes in nuclear architecture.
Figure 1. Nuclear assembly during mitosis and fertilization. (A) During mitotic exit, spindle disassembly is coordinated with chromosome decondensation and nuclear envelope formation. During fertilization, completion of female meiosis II follows largely the same events, with disassembly of the meiotic spindle and assembly of the maternal pronucleus; the only major difference is that one meiotic daughter cell is extruded as a polar body (not pictured). (B) Fertilization also requires the dramatic conversion of compact sperm chromatin into decondensed spherical pronuclei. Concomitantly, astral microtubules nucleated from sperm centrosomes capture both sperm and egg pronuclei and transport them toward one another at the center of the egg. â indicates sperm chromosomes and pronucleus, â indicates female pronucleus. (C) Nuclear (and pronuclear) assembly results in assembly of a double nuclear membrane and nuclear pore complexes around decondensed chromatin.
Figure 2. Pronuclear assembly in Xenopus egg extracts. (A) Sperm chromatin was added to metaphase egg extracts, released into interphase and visualized at the indicated time points with 1 μg/ml Hoechst 33342. (B) Fully assembled pronucleus at 60 min. DNA was visualized with Hoechst 33342; nuclear and endoplasmic-reticular membrane with 1 μM CM-DiI lipophilic dye; microtubules with 0.2 μM Alexa-Fluor-488 labeled bovine tubulin. Scale bars, 10 μm.
Figure 3. Dppa2 is required for nuclear shape and organized DNA replication. (A) Nuclei assembled in mock depleted and Dppa2-depleted Xenopus egg extracts were fixed at 60 min after release into interphase. DNA was visualized with Hoechst 33342 and replication by incorporation of 1 μM fluorescein labeled dUTP. Scale bar, 10 μm. (B) Chromatin-bound Dppa2 suppresses local microtubule assembly during nuclear formation. Microtubules play both positive (â+â) and negative (âââ) roles on nuclear formation.
Abrams,
Dynamic assembly of brambleberry mediates nuclear envelope fusion during early development.
2012, Pubmed
Abrams,
Dynamic assembly of brambleberry mediates nuclear envelope fusion during early development.
2012,
Pubmed
Akoumianaki,
Nucleocytoplasmic shuttling of soluble tubulin in mammalian cells.
2009,
Pubmed
Aravind,
SAP - a putative DNA-binding motif involved in chromosomal organization.
2000,
Pubmed
Asencio,
Coordination of kinase and phosphatase activities by Lem4 enables nuclear envelope reassembly during mitosis.
2012,
Pubmed
Beaudouin,
Nuclear envelope breakdown proceeds by microtubule-induced tearing of the lamina.
2002,
Pubmed
Belmont,
Real-time visualization of cell cycle-dependent changes in microtubule dynamics in cytoplasmic extracts.
1990,
Pubmed
,
Xenbase
Bortvin,
Incomplete reactivation of Oct4-related genes in mouse embryos cloned from somatic nuclei.
2003,
Pubmed
Buganim,
Single-cell expression analyses during cellular reprogramming reveal an early stochastic and a late hierarchic phase.
2012,
Pubmed
Chaudhary,
Stepwise reassembly of the nuclear envelope at the end of mitosis.
1993,
Pubmed
Crasta,
DNA breaks and chromosome pulverization from errors in mitosis.
2012,
Pubmed
Dechat,
Nuclear lamins.
2010,
Pubmed
Edens,
Nuclear size regulation: from single cells to development and disease.
2013,
Pubmed
,
Xenbase
Forbes,
Spontaneous formation of nucleus-like structures around bacteriophage DNA microinjected into Xenopus eggs.
1983,
Pubmed
,
Xenbase
Funabiki,
Making an effective switch at the kinetochore by phosphorylation and dephosphorylation.
2013,
Pubmed
Ganem,
Linking abnormal mitosis to the acquisition of DNA damage.
2012,
Pubmed
Gerlich,
Four-dimensional imaging and quantitative reconstruction to analyse complex spatiotemporal processes in live cells.
2001,
Pubmed
Haraguchi,
Live cell imaging and electron microscopy reveal dynamic processes of BAF-directed nuclear envelope assembly.
2008,
Pubmed
Hasegawa,
Chromosomal gain promotes formation of a steep RanGTP gradient that drives mitosis in aneuploid cells.
2013,
Pubmed
,
Xenbase
Hatch,
Catastrophic nuclear envelope collapse in cancer cell micronuclei.
2013,
Pubmed
Heald,
Mutations of phosphorylation sites in lamin A that prevent nuclear lamina disassembly in mitosis.
1990,
Pubmed
Heald,
Self-organization of microtubules into bipolar spindles around artificial chromosomes in Xenopus egg extracts.
1996,
Pubmed
,
Xenbase
Isermann,
Nuclear mechanics and mechanotransduction in health and disease.
2013,
Pubmed
Kelly,
Survivin reads phosphorylated histone H3 threonine 3 to activate the mitotic kinase Aurora B.
2010,
Pubmed
,
Xenbase
Kim,
Mouse B-type lamins are required for proper organogenesis but not by embryonic stem cells.
2011,
Pubmed
Kind,
Single-cell dynamics of genome-nuclear lamina interactions.
2013,
Pubmed
Laurell,
Phosphorylation of Nup98 by multiple kinases is crucial for NPC disassembly during mitotic entry.
2011,
Pubmed
Lemaitre,
Dynamics of the genome during early Xenopus laevis development: karyomeres as independent units of replication.
1998,
Pubmed
,
Xenbase
Levy,
Nuclear size is regulated by importin α and Ntf2 in Xenopus.
2010,
Pubmed
,
Xenbase
Lohka,
Formation in vitro of sperm pronuclei and mitotic chromosomes induced by amphibian ooplasmic components.
1983,
Pubmed
,
Xenbase
Lu,
Formation of the postmitotic nuclear envelope from extended ER cisternae precedes nuclear pore assembly.
2011,
Pubmed
Mitchison,
Growth, interaction, and positioning of microtubule asters in extremely large vertebrate embryo cells.
2012,
Pubmed
,
Xenbase
Nakamura,
Essential roles of ECAT15-2/Dppa2 in functional lung development.
2011,
Pubmed
Newport,
A major developmental transition in early Xenopus embryos: I. characterization and timing of cellular changes at the midblastula stage.
1982,
Pubmed
,
Xenbase
Ohsugi,
Kid-mediated chromosome compaction ensures proper nuclear envelope formation.
2008,
Pubmed
Peter,
In vitro disassembly of the nuclear lamina and M phase-specific phosphorylation of lamins by cdc2 kinase.
1990,
Pubmed
Qian,
PP1/Repo-man dephosphorylates mitotic histone H3 at T3 and regulates chromosomal aurora B targeting.
2011,
Pubmed
Ramadan,
Cdc48/p97 promotes reformation of the nucleus by extracting the kinase Aurora B from chromatin.
2007,
Pubmed
,
Xenbase
Rothballer,
SnapShot: The nuclear envelope I.
2012,
Pubmed
Rowat,
Nuclear envelope composition determines the ability of neutrophil-type cells to passage through micron-scale constrictions.
2013,
Pubmed
Salina,
Cytoplasmic dynein as a facilitator of nuclear envelope breakdown.
2002,
Pubmed
Schirmer,
Nuclear membrane proteins with potential disease links found by subtractive proteomics.
2003,
Pubmed
Schlaitz,
REEP3/4 ensure endoplasmic reticulum clearance from metaphase chromatin and proper nuclear envelope architecture.
2013,
Pubmed
Schmitz,
Live-cell imaging RNAi screen identifies PP2A-B55alpha and importin-beta1 as key mitotic exit regulators in human cells.
2010,
Pubmed
Schooley,
Building a nuclear envelope at the end of mitosis: coordinating membrane reorganization, nuclear pore complex assembly, and chromatin de-condensation.
2012,
Pubmed
Siegel,
Functional dissection of XDppa2/4 structural domains in Xenopus development.
2009,
Pubmed
,
Xenbase
Smyth,
Phosphoregulation of STIM1 leads to exclusion of the endoplasmic reticulum from the mitotic spindle.
2012,
Pubmed
Solovei,
LBR and lamin A/C sequentially tether peripheral heterochromatin and inversely regulate differentiation.
2013,
Pubmed
Song,
Microtubule-dependent regulation of mitotic protein degradation.
2014,
Pubmed
Sutovsky,
Assembly of nuclear pore complexes and annulate lamellae promotes normal pronuclear development in fertilized mammalian oocytes.
1998,
Pubmed
,
Xenbase
Tang,
Gene copy-number alterations: a cost-benefit analysis.
2013,
Pubmed
Teixeira,
Ubiquitin ligases and cell cycle control.
2013,
Pubmed
Tsai,
Aurora A kinase-coated beads function as microtubule-organizing centers and enhance RanGTP-induced spindle assembly.
2005,
Pubmed
,
Xenbase
Tseng,
Dual detection of chromosomes and microtubules by the chromosomal passenger complex drives spindle assembly.
2010,
Pubmed
,
Xenbase
Vagnarelli,
Repo-Man coordinates chromosomal reorganization with nuclear envelope reassembly during mitotic exit.
2011,
Pubmed
Verde,
Regulation of microtubule dynamics by cdc2 protein kinase in cell-free extracts of Xenopus eggs.
1990,
Pubmed
,
Xenbase
Wright,
Sperm nuclear activation during fertilization.
1999,
Pubmed
Wühr,
A model for cleavage plane determination in early amphibian and fish embryos.
2010,
Pubmed
,
Xenbase
Xue,
Chromatin-bound Xenopus Dppa2 shapes the nucleus by locally inhibiting microtubule assembly.
2013,
Pubmed
,
Xenbase
